BackgroundDengue, a mosquito-borne viral disease, poses a significant global public health risk. In tropical countries such as India where periodic dengue outbreaks can be correlated to the high prevalence of the mosquito vector, circulation of all four dengue viruses (DENVs) and the high population density, a drug for dengue is being increasingly recognized as an unmet public health need.Methodology/Principal findingsUsing the knowledge of traditional Indian medicine, Ayurveda, we developed a systematic bioassay-guided screening approach to explore the indigenous herbal bio-resource to identify plants with pan-DENV inhibitory activity. Our results show that the alcoholic extract of Cissampelos pariera Linn (Cipa extract) was a potent inhibitor of all four DENVs in cell-based assays, assessed in terms of viral NS1 antigen secretion using ELISA, as well as viral replication, based on plaque assays. Virus yield reduction assays showed that Cipa extract could decrease viral titers by an order of magnitude. The extract conferred statistically significant protection against DENV infection using the AG129 mouse model. A preliminary evaluation of the clinical relevance of Cipa extract showed that it had no adverse effects on platelet counts and RBC viability. In addition to inherent antipyretic activity in Wistar rats, it possessed the ability to down-regulate the production of TNF-α, a cytokine implicated in severe dengue disease. Importantly, it showed no evidence of toxicity in Wistar rats, when administered at doses as high as 2g/Kg body weight for up to 1 week.Conclusions/SignificanceOur findings above, taken in the context of the human safety of Cipa, based on its use in Indian traditional medicine, warrant further work to explore Cipa as a source for the development of an inexpensive herbal formulation for dengue therapy. This may be of practical relevance to a dengue-endemic resource-poor country such as India.

The quality control of medicinal herbs post harvesting or after collection becomes very critical because of susceptibility to fungal invasion during storage depending on the temperature and humidity of the storage area. The information on moisture equilibrium is important on the process and storage of foods which can be extended to medicinal herbs. In the present study, the growth of Aspergillus flavus was observed on selected ten medicinal herbs with water activity aw above 0.81 when stored at 25 +/- 2 degrees C, 30 +/- 2 degrees C and 40 +/- 2 degrees C except for Picrorhiza kurrooa and Alpinia galanga which were found to have anti-fungal properties. Aspergillus flavus did not grow in any samples of medicinal herbs with water activity aw below 0.81 at temperatures of 25 +/- 2 degrees C, 30 +/- 2 degrees C and 40 +/- 2 degrees C. Also Aspergillus flavus did not grow in any samples of medicinal herbs with water activity aw above 0.81 when stored below 10 +/- 2 degrees C. Therefore it can be concluded that the contamination of medicinal herbs with aflatoxins can be minimized by controlling water activity and storage temperature. Sorption isotherms (desorption) can be interpreted to determine the optimum drying which can lower the water activity to the level required for preventing growth of Aspergillus flavus and also for ensuring quality of medicinal herbs which may get destroyed upon over drying. Furthermore, it also saves incremental cost in prolonged drying over the optimum drying.